Mortuary + Shilgengar, Sire of Famine + Bolas's Citadel + Serrated Scorpion

Mortuary

Shilgengar, Sire of Famine

Bolas's Citadel

Serrated Scorpion

How it works

1. Activate Shilgengar by sacrificing Serrated Scorpion.
2. When Serrated Scorpion dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Serrated Scorpion from your graveyard onto the top of your library.
4. Resolve the Serrated Scorpion trigger, causing you to gain 2 life and dealing 2 damage to each opponent.
5. Resolve the Shilgengar ability.
6. Cast Serrated Scorpion from the top of your library by paying 1 life due to Bolas's Citadel.
7. Repeat.

This loop turns Shilgengar, Sire of Famine into an infinite blood-and-death engine by using Mortuary to instantly recycle any sacrificed creature back to the top of your library. From there, Bolas's Citadel allows you to bypass mana costs entirely, letting you replay the sacrificed creature straight from the top of your deck by simply paying life instead. Finally, Serrated Scorpion acts as the perfect catalyst and payoff for this cycle—its death triggers not only fuel the loop, but the life it drains and returns completely offsets the life you pay to the Citadel, allowing you to drain your opponents out of the game infinitely.